//
// Written by Curtis Olson, started July 1997.
//
-// Copyright (C) 1997 Curtis L. Olson - curt@infoplane.com
+// Copyright (C) 1997 Curtis L. Olson - http://www.flightgear.org/~curt
//
// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Library General Public
// $Id$
+/*
+ A C-program for MT19937, with initialization improved 2002/2/10.
+ Coded by Takuji Nishimura and Makoto Matsumoto.
+ This is a faster version by taking Shawn Cokus's optimization,
+ Matthe Bellew's simplification, Isaku Wada's real version.
+
+ Before using, initialize the state by using init_genrand(seed)
+ or init_by_array(init_key, key_length).
+
+ Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
+ All rights reserved.
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions
+ are met:
+
+ 1. Redistributions of source code must retain the above copyright
+ notice, this list of conditions and the following disclaimer.
+
+ 2. Redistributions in binary form must reproduce the above copyright
+ notice, this list of conditions and the following disclaimer in the
+ documentation and/or other materials provided with the distribution.
+
+ 3. The names of its contributors may not be used to endorse or promote
+ products derived from this software without specific prior written
+ permission.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
+ CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
+ EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
+ PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
+ NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+
+ Any feedback is very welcome.
+ http://www.math.keio.ac.jp/matumoto/emt.html
+ email: matumoto@math.keio.ac.jp
+*/
+
#ifdef HAVE_CONFIG_H
-# include <config.h>
+# include <simgear_config.h>
#endif
#include <stdio.h>
#include "sg_random.h"
-#ifndef HAVE_RAND
-# ifdef sgi
-# undef RAND_MAX
-# define RAND_MAX 2147483647
-# endif
-#endif
+/* Period parameters */
+#define N 624
+#define M 397
+#define MATRIX_A 0x9908b0dfUL /* constant vector a */
+#define UMASK 0x80000000UL /* most significant w-r bits */
+#define LMASK 0x7fffffffUL /* least significant r bits */
+#define MIXBITS(u,v) ( ((u) & UMASK) | ((v) & LMASK) )
+#define TWIST(u,v) ((MIXBITS(u,v) >> 1) ^ ((v)&1UL ? MATRIX_A : 0UL))
+
+static unsigned long state[N]; /* the array for the state vector */
+static int left = 1;
+static int initf = 0;
+static unsigned long *next;
-#ifdef __SUNPRO_CC
- extern "C" {
- long int random();
- void srandom(unsigned int seed);
+/* initializes state[N] with a seed */
+void init_genrand(unsigned long s)
+{
+ int j;
+ state[0]= s & 0xffffffffUL;
+ for (j=1; j<N; j++) {
+ state[j] = (1812433253UL * (state[j-1] ^ (state[j-1] >> 30)) + j);
+ /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
+ /* In the previous versions, MSBs of the seed affect */
+ /* only MSBs of the array state[]. */
+ /* 2002/01/09 modified by Makoto Matsumoto */
+ state[j] &= 0xffffffffUL; /* for >32 bit machines */
}
-#endif
+ left = 1; initf = 1;
+}
+
+static void next_state(void)
+{
+ unsigned long *p=state;
+ int j;
+
+ /* if init_genrand() has not been called, */
+ /* a default initial seed is used */
+ if (initf==0) init_genrand(5489UL);
+
+ left = N;
+ next = state;
+
+ for (j=N-M+1; --j; p++)
+ *p = p[M] ^ TWIST(p[0], p[1]);
+ for (j=M; --j; p++)
+ *p = p[M-N] ^ TWIST(p[0], p[1]);
+
+ *p = p[M-N] ^ TWIST(p[0], state[0]);
+}
// Seed the random number generater with time() so we don't see the
// same sequence every time
void sg_srandom_time() {
-#ifdef HAVE_RAND
- srand(time(NULL));
-#else
- srandom(time(NULL));
-#endif
+ init_genrand(time(NULL));
}
// Seed the random number generater with your own seed so can set up
// repeatable randomization.
void sg_srandom( unsigned int seed ) {
-#ifdef HAVE_RAND
- srand( seed );
-#else
- srandom( seed );
-#endif
+ init_genrand( seed );
}
// return a random number between [0.0, 1.0)
double sg_random() {
-#ifdef HAVE_RAND
- return(rand() / (double)RAND_MAX);
-#else
- return(random() / (double)RAND_MAX);
-#endif
+ unsigned long y;
+
+ if (--left == 0)
+ next_state();
+ y = *next++;
+
+ /* Tempering */
+ y ^= (y >> 11);
+ y ^= (y << 7) & 0x9d2c5680UL;
+ y ^= (y << 15) & 0xefc60000UL;
+ y ^= (y >> 18);
+
+ return (double)y * (1.0/4294967295.0);
+ /* divided by 2^32-1 */
}
projects / simgear.git / blobdiff